FIG. 1 is a diagram showing a composition architecture of an Evolved Packet System (EPS) of the 3rd Generation Partnership Project (3GPP) according to the related art. As shown in FIG. 1, the network architecture of the EPS in a non-roaming scenario includes an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), a Mobility Management Entity (MME), a Serving Gateway (S-GW), a Packet Data Network Gateway (P-GW), a Home Subscriber Server (HSS), a Policy and Charging Rules Function (PCRF) entity and other support nodes.
The PCRF is the core of Policy and Charging Control (PCC) and is responsible for making a policy decision and a charging rule. The PCRF provides network control rules based on service data streams, and the network control mainly includes service data stream detection, gating control, control for Quality of Service (QoS), a charging rule based on the data streams and the like. The PCRF sends the policy and the charging rule made thereby to a Policy and Control Enforcement Function (PCEF) entity for execution, and at the same time, the PCRF may further need to ensure that these rules are consistent with the subscription information of a user. The basis of making a policy and a charging rule by the PCRF includes: the information related to a service acquired from an Application Function (AF); the policy and charging control subscription information of the user acquired from a Subscription Profile Repository (SPR); and the information of a network related to a bearer acquired from the PCEF.
The EPS supports the interworking with a non-3GPP system, which is implemented through an S2a/b/c interface. The P-GW serves as an anchor between a 3GPP system and a non-3GPP system. As shown in FIG. 1, the non-3GPP system is divided into a trusted non-3GPP IP access network and a non-trusted non-3GPP IP access network. The trusted non-3GPP IP access network can be connected to the P-GW directly through an S2a interface. The non-trusted non-3GPP IP access network needs to pass through an Evolved Packet Data Gateway (ePDG) to be connected to the P-GW, and the interface between the ePDG and the P-GW is an S2b interface. Signalling and data between a User Equipment (UE) and an ePDG are encrypted for protection through an Internet Protocol Security (IPSec). An S2c interface provides control and mobility support related to a user plane between the UE and the P-GW, and the mobility management protocol supported by the S2c interface is mobile IPv6 supporting double stacks (i.e. DSMIPv6).
At present, many operators are concerned about the Fixed Mobile Convergence (FMC) technology very much and have studied the interconnection and interworking technology of the 3GPP and the Broadband Forum (BBF).
FIG. 2 is a diagram showing a roaming architecture of a home router in a policy interworking scenario in which a UE accesses a 3GPP core network through a BBF access network according to the related art. As shown in FIG. 2, the BBF access network is regarded as the non-trusted non-3GPP IP access network. The user accesses a mobile core network through the BBF access network. At present, there are two service ways based on the architecture. One way is that the service accessed by the UE needs to be routed back to the EPC, which way is called Evolved Packet Core (EPC) routed. The other way is that the service accessed by the UE is not routed back to the EPC, but directly routed to a service network from a BBF network, which way is called a Non-seamless WLAN Offload (NSWO). In the roaming scenario in FIG. 2, the BBF access network needs to implement interworking with a Home PLMN (HPLMN) through a Visited Public Land Mobile Network (VPLMN), including authentication, data routing, policy control and the like.
FIG. 3 is a diagram showing the roaming architecture of a home router in a policy convergence scenario in which a UE accesses a 3GPP core network through a BBF access network according to the related art. As shown in FIG. 3, the difference between FIG. 2 and FIG. 3 mainly lies in that the BBF access network and the VPLMN usually belong to a same operator, a Visit PCRF (V-PCRF) supports the interaction with an IP edge through a Gxd interface, and a Home PCRF (H-PCRF) needs to interact with the BBF access network through the V-PCRF.
FIG. 4 is a diagram showing the attachment flow when a UE accesses a 3GPP core network through a fixed broadband access network according to the related art. As shown in FIG. 4, which is a diagram showing the attachment flow when a UE accesses a 3GPP network through the PMHV6 protocol based on the architecture diagram shown in FIG. 2. In the FIG. 4, a GPRS Tunnel Protocol (GTP) is adopted between the ePDG and the P-GW, and the flow includes the following steps.
Step S402: A UE accesses a BBF access system to execute 3GPP-based access authentication. A BBF AAA interacts with a 3GPP AAA server through a 3GPP AAA proxy (or an AAA server further interacts with an HSS) to complete EAP authentication.
Step S404: The UE acquires a local IP address allocated by the BBF access network.
Step S406: Triggered by Step S402 or S404, a BPCF is notified of the access of the UE through the BBF access network.
Step S408: When the BPCF receives triggering and supports policy interworking with the PCRF, the BPCF sends a CCR message to the V-PCRF to request for establishing an S9a* session if a local policy indicates that policy control for NSWO traffic can be provided to the user, wherein the CCR message carries a user identifier, a local IP address of the UE and NSWO-APN.
Step S410: When determining that the S9 session of the user has not been established yet, the V-PCRF sends a CCR message (an S9 session establishment message) to an H-PCRF to request for establishing the S9 session and an S9 sub-session, wherein the sub-session contains an information user identifier, a local IP address of the UE and NSWO-APN. The V-PCRF saves the corresponding relationship between the S9a* session and the S9 sub-session. The S9 sub-session is used for the policy control of the NSWO traffic.
Step S412: The H-PCRF returns an acknowledgement message (i.e., a CCA message) after making a policy decision and sends the policy to the V-PCRF through the S9 sub-session.
Step S414: The V-PCRF further sends the policy to the BPCF through the CCA message.
Step S416: The UE dynamically selects an ePDG in a visited network, initiates an IKEv2 tunnel establishment process and carries out authentication through EAP. The ePDG acquires a local IP address of the UE.
Step S418: The ePDG selects a P-GW and sends a session establishment request message to the selected P-GW, wherein the message carries a user identifier, a local IP address of the UE and the like. After receiving the request message, the P-GW allocates an EPC IP address to the UE to establish a binding context.
Step S420: The PCEF in the P-GW sends an IP-CAN session establishment indication message to the H-PCRF, wherein the message carries a user identifier, a PDN identifier, a local IP address of the UE and a UE EPC IP address. The H-PCRF carries out QoS authorization according to the user identifier and other information and returns an acknowledgement message to the PCEF.
Step S422: The P-GW sends a P-GW IP address update message to an AAA server and sends the address of the P-GW to the AAA server. The AAA server further interacts with the HSS, and the HSS saves the address of the P-GW.
Step S424: The P-GW returns a session establishment acknowledgement message to the ePDG, wherein the message carries an EPC IP address.
Step S426: After the proxy binding is updated successfully, an IPSec tunnel is established between the UE and the ePDG.
Step S428: The ePDG sends the last IKEv2 signalling to the UE, wherein the signalling carries an IP address of the UE.
Step S430: Triggered by Step S418, the H-PCRF sends an RAR message (an S9 sub-session establishment triggering message) to the V-PCRF to trigger the establishment of an S9 sub-session for the policy control of EPC-routed traffic when determining that the S9 session has been established for the user, wherein the message carries a user identifier, an APN and a local IP address of the UE.
Step S432: The V-PCRF returns an RAA message to the H-PCRF, i.e., the V-PCRF returns an acknowledgement message to the H-PCRF.
Step S434: The V-PCRF sends a CCR message (an S9 session modification message) to the H-PCRF to modify the S9 session and establish an S9 sub-session, wherein the sub-session is used for the policy control of EPC-routed traffic.
Step S436: The H-PCRF returns a CCA message to the V-PCRF to confirm the S9 session modification message.
Step S438: Triggered by Step S430, the V-PCRF sends a TER message to the BPCF to trigger the establishment of an S9a session, wherein the message carries a user identifier and an IP address of the UE.
Step S440: The BPCF returns a TEA message to the V-PCRF to confirm the S9a session establishment triggering message.
Step S442: The BPCF sends a CCR message to the V-PCRF to request for establishing an S9a session.
Step S444: The V-PCRF returns a CCA message to the BPCF to confirm the establishment of the S9a session.
Step S446: The BPCF provides a policy to an IP edge.
In the Steps above, in Step S430, it is assumed that the H-PCRF has received the CCR message sent in Step S410, namely, S9 session has been established. However, Step S406 and Step S416 may be concurrent actually. Therefore, the H-PCRF may have received the message sent in Step S418 before receiving the message sent in Step S406. Because no S9 session is established, the H-PCRF may send an S9 session triggering message to the V-PCRF. However, after the message is sent, the H-PCRF receives an S9 session establishment message for the establishment of S9 sub-session of the NSWO. Thus, the V-PCRF may think the H-PCRF executes a wrong flow.
To avoid conflict in the process of establishing the S9 sub-session in the related art, there is still no effective solution.